State-of-the-art in radiation oncology treatments use 6 MeV to 20 MeV X-ray doses from linear accelerator systems. The systems are configured to provide dose rates that allow treatment of a cancer patient in term of “fractions”, which refers to the dose in any given treatment session for a patient. For example, a dose rate of 10 Gy/minute at 1 meter from the linear accelerator is used for some 6 MeV systems.
The most current linear accelerator systems, such as those from Varian, Elekta, and Accuray generally include some form of X-ray imaging as part of the system, for the purpose of providing some form of image of a patient's tumor with respect to the patient's other anatomical structures. Prior to treatment with a linear accelerator system, a standard course of the diagnosis and development of a treatment plan for a cancer patient also includes developing patient images by high quality imaging machines in order to determine the size and position of a tumor or tumors to be treated with the X-ray dose. Imaging prior to radiation treatment can be performed with dedicated imaging systems such as fan-beam CT (computed tomography) scanners, an MRI (magnetic resonance imaging) system, and/or a PET (positron emission tomography) scanner, with some PET scanners combining CT scanning within a single machine. Each imaging technique has its advantages and provides benefits in creating images that are later used for treating cancer with high energy X-rays. A further application of the fan-beam CT scanner is the ability to use a CT scan to correct for any inhomogeneity in a particular patient's tissues in order to optimize the radiation treatment plan. Thus, in a significant percentage of radiation oncology cases, a CT scan is used not only for the imaging of the tissue before treatment but also for correcting for tissue inhomogeneity in terms of Hounsfield units. These imaging techniques are well known to radiation oncologists.
State-of-the-art machines that contain linear accelerators for the purpose of generating radiation to treat the patients include imaging as well, but typically in the form of either two-dimensional X-ray imaging, or what is known as “cone beam” CT imaging. These imaging techniques provide some information, but at a generally lower image quality compared to dedicated fan beam CT scanners or MRI machines. It is technologically challenging and expensive to incorporate high quality fan beam CT scanning or MRI into a linear accelerator system. These product combinations have proven unpopular, perhaps because of the expense of not only the machine, but also the need to create a special new vault for shielding medical personnel. Radiation therapy systems generate multiple sources of unwanted radiation are produced that provide a threat to operators, workers in adjacent areas, and the public. These sources of radiation consist of primary radiation that is transmitted through the patient, scatter radiation produced by the patient tissues and parts of the Radiotherapy system that are exposed to the primary radiation, and leakage radiation from the X-ray generating and collimating components of the system.
Treatment rooms, or vaults or bunkers, used in radiation oncology include extensive shielding to protect medical personnel as well as the public from the radiation generated while treating the cancer patient. Such shielding is most often made of concrete, although lead and steel and other materials can also be used when a smaller footprint is required or when limited by external dimensions. For an energy of 6 MeV and dose of 10 Gy/min, a thickness of several feet of concrete shielding is typically used. Such vaults typically cost at least $1,000,000, or $2,000,000 or more to shield a single multi-MeV level radiation oncology system and to finish the room to a standard that is suitable for treating patients.
Because of the cost of such conventional systems, including the vault or bunker, the availability of these devices is limited. Typically, only large hospitals are able to utilize these devices often enough to justify the costs of offering such radiotherapy services. This, in turn, restricts the availability of these devices to highly populated areas. Moreover, even in highly populated areas, a group of related medical facilities will install such radiotherapy systems at only one or two of their facilities. In such instances, patients requiring radiotherapy treatment frequently are required to travel significant distances to receive their treatment. In many instances the burden of such travel is borne by the patient, but in other instances, the hospital must arrange transport of the patient to the treatment facility. These ongoing costs are significant, to say nothing of the stress on a patient who is already suffering from a serious illness.
The challenge is even greater outside of developed countries with large urban populations. There are approximately 7,600 radiotherapy facilities in the world (2300 in the USA) while approximately 60,000 CT scanners are available worldwide at facilities that provide imaging services. A reasonable assumption is that every radiotherapy facility in a developed country utilizes an average of 2.5 CT scanners. Thus, it is reasonable to estimate that there are 41,000 CT scanners in facilities that do not presently provide radiotherapy. Some, perhaps many, of these centers are in developing, rural, or under-served parts of the world. In such areas, it is reasonable to assume an average of 1.5 CT scanners per facility. From this, it can be estimated that there are over 27,000 facilities worldwide with access to CT imaging, but without radiotherapy. It is likely that, if the costs for providing radiotherapy treatments locally were manageable, such as by reducing the need for a vault, and/or reducing the cost of the radiotherapy system itself, a significant number of these facilities would seek to improve the lives of the patients in their care by installing such a radiotherapy system.
Another factor that perhaps limits the number of installations offering radiotherapy for cancer patients is the difficulty in mating high resolution images to linac-based X-ray sources. It is well understood that, for a variety of reasons, fan beam CT imagers at present offer the best spatial and contrast resolution. The greater detail offered by such imagers is significant, since such images permit the implementation of greatly improved image-guided radiotherapy, or IGRT. In conventional IGRT, a fan beam CT scan is made well in advance of the day of treatment, frequently at a different facility than where treatment will occur. Then, on treatment day, the CT-generated image is used to position the patient for treatment. However, because it has historically been difficult to combine a fan beam CT imager with a linac-based X-ray source, verification of the patient's position is made using a cone beam CT scanner. Cone beam CT scanners have thus far proven incapable of providing image quality equivalent to a fan beam CT scanner. Thus, while the lower resolution and generally inferior image quality provided by cone beam CT scanners is currently used for verification of patient position, the resulting image matching process has significant potential for error due not only to the lower quality of the day-of-treatment cone beam CT scans compared to the diagnostic fan beam CT scans, but also of the difference in time and location. Thus, the higher quality images that would be possible if the radiotherapy system comprised a fan beam CT imager integrated together with an X-ray source would plainly offer significant benefits for both the patient and the treating medical team.
Therefore, that has been a need for a radiation oncology system that combines both a true fan beam CT imager with a linac-based oncology X-ray system.
Further, there has been a need for a radiation oncology system which can be used in the treatment of a significant percentage of oncology cases, yet does not require the construction of a conventional vault.
There is a need for a novel new product for the treatment of cancer that takes advantage of high quality imaging systems that are already available, especially fan beam CT scanners.
There is a need for an X-ray linac system, capable of outputting sufficient energy for the treatment of a substantial number of cancers, for example 6 MeV, that does not require a conventional vault or bunker. The new system would be self-shielded or only require minimal and economical room modification.
There is a need for a 6 MeV X-ray linac system for the treatment of cancer that can treat as many as 90% of all types of cancers, but that costs less than 50% of existing solutions.
There is a need for a 6 MeV X-ray linac system for the treatment of cancer that is designed to work with a fan beam CT scanner, sharing a treatment couch, for the purpose of high quality imaging of the patient immediately prior to radiation treatment, which will improve accuracy of the treatment. The fan beam CT scanner may be pre-existing at a facility, before the installation of the new 6 MeV X-ray linac system.